The invention relates to devices and methods for the administration or delivery of substances, including the administration of medicinal substances to patients. More particularly, it relates to injection or infusion devices and methods, and to an auto-injector for automatically injecting an active agent. In one embodiment, the auto-injector comprises an elongated casing, an injection needle which can be shifted axially in the casing and is connected to an active agent container, a piston which can be shifted in the active agent container for the purpose of delivering the active agent, and a needle protecting tube which can be shifted relative to the casing.
Auto-injectors are known in many different embodiments. They serve to administer injections, in particular by a patient him or herself. When used, an injection needle is automatically inserted, in the majority of cases by means of a spring force, and then an active agent is injected. Many reusable auto-injectors are known and also those which, once used, are partially or completely thrown away. Auto-injectors which are sold or distributed filled and with the springs tensed have to be provided with a needle protecting cap in order to be able to ensure the sterility of the injection needle. Since this needle protecting cap preferably encloses the active agent container connected to the injection needle, forming a seal, a certain tensile force is necessarily exerted on the active agent container as the needle protecting cap is removed in preparation for using the auto-injector.